Coffee, Caffeine, and Risk of Type 2
Diabetes ::A
A prospective cohort study in
younger and middle-aged U.S. women
Rob M. van Dam, PHD
Department of Nutrition, Harvard School of Public Health,
B os ton, M as s achus etts
Diabetes Care 2 9 : 3 9 8 -4 0 3 , 2 0 0 6
Coffee Consumption and Risk of Type 2 Diabetes
Mellitus: An 11-Year Prospective Study of
28 812 Postmenopausal Women
Mark A. Pereira, PhD; Emily D. Parker,
MPH; Aaron R. Folsom, MD
Arch Intern Med. 2006;166:1311-1316.
INTRODUCTION
• High coffee consumption has been associated with better
glucose tolerance and a substantially lower risk of type 2
diabetes in diverse populations in Europe, the U.S., and
Japan
• Short-term metabolic studies in humans have shown that
caffeine can acutely lower insulin sensitivity.However,
the long-term effects of caffeine intake on glucose
metabolism are unknown
• In most of the populations in which the relation
between coffee consumption and type 2 diabetes
has been studied, drip-filtered caffeinated coffee
was the predominant type of coffee consumed .
• In addition, in previous studies consumption of
five or more cups of coffee per day was
consistently associated with a lower risk of type 2
diabetes, but results for lower levels of
consumption have been mixed .
RESEARCH DESIGN AND METHODS
• Iowa Women's Health Study
• In January 1986, a random sample of 99 826 women
aged 55 to 69 years with a valid Iowa driver's license
were mailed a 16-page questionnaire and invited to
participate in the study.
• The original study sample consisted of 41 836 women
who returned the baseline questionnaire.
• Finally, 28 812 postmenopausal women free of diabetes
and cardiovascular disease in the general community.
• Women were excluded from our analysis if they reported
implausibly high (>5000 kcal) or low (<600 kcal) energy
intakes, left 30 or more items blank on the food frequency
questionnaire, or had diabetes, cardiovascular disease, or
cancer (other than nonmelanoma skin cancer) at baseline,
or were unsure whether they had diabetes.
• A 127-item food frequency questionnaire was used to
assess past-year typical food intake.
• Women were asked "Please fill in your average use
during the past year, of each specified food." For
"decaffeinated coffee" and "coffee," the standard serving
size was assigned on the questionnaire as "1 cup," and the
intake frequency options ranged from "never or less than
once per month" up to "6 or more cups per day."
RESULTS
• During 11 years of follow-up, there were 1418
incident cases of diabetes.
• During 866,118 person-years of follow-up, we
documented 1,263 cases of type 2 diabetes.
RESEARCH DESIGN AND METHODS
• Nurses’ Health Study II. This cohort included 116,671
female U.S. nurses at study initiation in 1989
• Participants: aged 26–46 years at the start of follow-up.
• We excluded women if they did not complete a dietary
questionnaire in 1991;
• if >70 items were left blank or
• if the reported total energy intake was implausible (<500
kcal/day or >3,500 kcal/day);
• if they had a history of diabetes (including gestational
diabetes), cancer (except nonmelanoma skin cancer), or
cardiovascular disease at baseline; or if they had not
provided data on physical activity in 1991.
RESEARCH DESIGN AND METHODS
• A total of 88,259 women remained for the current
analysis.
• Participants were asked how often on average
during the previous year they had consumed
1. caffeinated and decaffeinated coffee ("one cup"),
tea ("one cup or glass"),
2. different types of caffeinated soft drinks ("one
glass, bottle, or can"),
3. and chocolate products (e.g., "bar or packet").
• choose 9 responses (<1/m, 1-3/m, 1/wk, 2-4/wk, 56/wk, 1/d, 2-3/d, 4-5/d, and >5/d).
RESEARCH DESIGN AND METHODS
• usual method of preparing coffee with the answer
categories "mainly filtered," "mainly instant,"
"mainly espresso or perculator," and "no usual
method/don’t know/don’t use."
• usual method of preparing coffee with the answer
categories "mainly filtered," "mainly instant,"
"mainly espresso or perculator," and "no usual
method/don’t know/don’t use."
CONCLUSIONS
• Coffee intake, especially decaffeinated, was inversely
associated with risk of type 2 diabetes mellitus in this
cohort of postmenopausal women.
• women aged 26–46 years at baseline, consumption of
two or more cups of coffee per day was associated with
a substantially lower risk of type 2 diabetes during 10
years of follow-up
• This association was similar for caffeinated and
decaffeinated coffee and for filtered and instant coffee.
• The inverse association between coffee consumption
and risk of type 2 diabetes was independent of caffeine
intake.
Discussion
• Coffee has strong antioxidant properties in vivo ,
chlorogenic acid may delay glucose absorption in
the intestine , and intake of coffee components
improved glucose metabolism in rats.
• Instant coffee consumption was also inversely
associated with risk of type 2 diabetes is plausible
as the composition is similar to drip-filtered
coffee
• Causal effects on insulin sensitivity and/or insulin
secretion from a variety of minerals, antioxidants, and
phytochemical compounds found in coffee.
• Higher consumption of unfiltered Scandinavian potboiled coffee is associated with a lower risk of type 2
diabetes. However, high consumption of unfiltered
coffee increases plasma LDL concentrations and may
thus increase risk of coronary heart disease.
• Consumption of decaffeinated coffee may reduce risk of
type 2 diabetes, while avoiding potential detrimental
effects on blood pressure and sleep quality.
• Caffeine and coffee may have beneficial effects
on bladder dysfunction in the early stage of
diabetes by increasing cAMP content in the lower
urinary tract, recovering the micturition reflex and
improving the detrusor contractility
• Coffee extract blocked 11beta-HSD1-dependent
cortisol formation, prevented the subsequent
nuclear translocation of the glucocorticoid
receptor and abolished glucocorticoid-induced
expression of the key gluconeogenic enzyme
phosphoenolpyruvate carboxykinase.